This invention relates to gastrin and cholecystokinin (CCK) receptor ligands. The invention also relates to methods for preparing such ligands and to compounds that are useful intermediates in such methods. The invention further relates to pharmaceutical compositions comprising such ligands and methods for preparing such pharmaceutical compositions.
The gastrins and cholecystokinins are structurally related neuropeptides that exist in gastrointestinal tissue, gastrinomas and, in the case of the cholecystokinins, the central nervous system (J. H. Walsh, Gastrointestinal Hormones, L. R. Johnson, ed., Raven Press, New York, 1994, p. 1).
Several forms of gastrin are found including 34-, 17- and 14-amino acid species with the minimum active fragment being the C-terminal tetrapeptide (TrpMetAspPhe-NH2), which is reported in the literature to have full pharmacological activity (H. J. Tracy and R. A. Gregory, Nature (London), 1964, 204:935-938). Much effort has been devoted to the synthesis of analogs of this tetrapeptide (and the N-protected derivative Boc-TrpMetAspPhe-NH-2) in an attempt to elucidate the relationship between structure and activity.
Natural cholecystokinin is a 33 amino acid peptide (CCK-33, the C-terminal 5 amino acids of which are identical to those of gastrin. Also found naturally is the C-terminal octapeptide (CCK-8) of CCK-33. A review of CCK receptors, ligands and the activities thereof may be found in P. de Tullio et al, (Exp. Opin. Invest. Drugs, 2000, 9(1): 129-146).
Gastrin and cholecystokinin are key regulators of gastrointestinal function. In addition, cholecystokinin is a neurotransmitter in the brain. Gastrin is one of the three primary stimulants of gastric acid secretion. In addition to the acute stimulation of gastric acid, gastrin has a trophic effect on the gastrointestinal mucosa and is implicated as a trophic hormone of several adenocarcinomas, including pancreatic, colorectal, esophageal and small cell lung.
Cholecystokinin stimulates intestinal motility, gallbladder contraction and pancreatic enzyme secretion, and is known to have trophic actions on the pancreas thus increasing, inter alia, pancreatic enzyme production. Cholecystokinin also inhibits gastric emptying and has various effect in the central nervous system, including regulation of appetite and pain.
Gastrin acts on CCK2 (otherwise known as gastrin/CCK-B receptors) whereas cholecystokinin acts on both CCK2 and CCK1 receptors (otherwise known as cholecystokinin/CCK-A receptors). Compounds that bind to cholecystokinin and/or gastrin receptors are important because of their potential pharmaceutical use as antagonists of the natural peptides or mimetics of the natural peptides acting as partial or full agonists at the cholecystokinin and/or gastrin receptors. A selective gastrin receptor antagonist has not yet been marketed. However, several are currently undergoing clinical evaluation. JB95008 (gastrazole) is being developed by The James Black Foundation and Johnson & Johnson for the potential treatment of advanced pancreatic cancer (pancreatic adenocarcinoma), and is currently in Phase II clinical trails. ML Laboratories and Panos are developing L-365,260 (Colycade), which is in Phase II clinical trials for pain. Other potential indications included eating disorders and cancer. YF-476 (formerly YM-220), under join development by Yamanouchi and Ferring Research Institute, is in Phase I clinical trials for gastro-esophageal reflux disease (GERD). In Phase I trials, Zeria Pharmaceutical is investigating Z-360, an orally available 1,5-benzodiazepine derivative (WO-09825911), as a potential treatment for gastroduodenal ulcers and reflux esophagitis. CR 2945 (itriglumide), an orally active anthranilic acid derivative, has been investigated by Rotta in Phase I trials of anxiety disorders, cancer (particularly colon cancer) and peptic ulcer.
Gastrimmune, Aphton Corporation's anti-gastrin vaccine, which works by chemical neutralization of the hormone, is undergoing late stage clinical trials for cancer indications, in particular, pancreatic and gastric tumors.
In addition to those indications described above, gastrin (CCK2) antagonists have been proposed for the following gastrin-related disorders: gastrointestinal ulcers, Barrett's esophagus, antral G cell hyperplasia, pernicious anaemia, Zollinger-Ellison syndrome and other conditions in which lower gastrin activity or lower acid secretions is desirable.
Cholecystokinin (CCK1) receptors have been shown to mediate cholecystokinin-stimulated gallbladder contraction, pancreatic enzyme secretion, satiety, gastric emptying inhibition and regulation of peristalsis, indicating a key role in the integrated physiological gastrointestinal response to a meal. In addition, there is evidence that cholecystokinin receptors mediate a mitogenic action of cholecystokinin on some adenocarcinomas. Consequently, selective cholecystokinin receptor antagonists, for example, devazepide (Merck), lorglumide (Rotta), 2-NAP (JBF), dexloxiglumide (Rotta) and lintitript (Sanofi) have been examined in the clinic for potential applications in, inter alia, irritable bowel syndrome, chronic constipation, non-ulcer dyspepsia, acute and chronic pancreatitis, biliary disease and pancreatic cancer. Additional roles of cholecystokinin receptors include the regulation or appetite and metabolism, indicating potential therapeutic applications in the treatment of disorders such as obesity and anorexia nervosa. Other possible uses are in the potentiation of opiate (for example morphine) analgesia and in the treatment of cancers, especially of the pancreas. Moreover, ligands for cholecystokinin/gastrin receptors in the brain have been claimed to possess anxiolytic activity, and gastrin receptor antagonists would be expected to act as neurological agents towards the relief of anxiety and related neuroses and psychoses.